E and M signaling
TYPE OF SUPERVISORY LINE SIGNALING
E&M wink; E and M signalling
E and M signaling is a type of supervisory line signaling that uses DC signals on separate leads, called the "E" lead and "M" lead, traditionally used in the telecommunications industry between telephone switches. Various mnemonic names have been used to memorize these letters, such as Ear and Mouth, the most common variation.